import { OB11EmitEventContent } from './index';
import { Request, Response } from 'express';
import { OB11HttpServerAdapter } from './http-server';

export class OB11HttpSSEServerAdapter extends OB11HttpServerAdapter {
  private sseClients: Response[] = [];

  override async handleRequest (req: Request, res: Response) {
    if (req.path === '/_events') {
      this.createSseSupport(req, res);
    } else {
      super.httpApiRequest(req, res, true);
    }
  }

  private async createSseSupport (req: Request, res: Response) {
    res.setHeader('Content-Type', 'text/event-stream');
    res.setHeader('Cache-Control', 'no-cache');
    res.setHeader('Connection', 'keep-alive');
    res.flushHeaders();

    this.sseClients.push(res);
    req.on('close', () => {
      this.sseClients = this.sseClients.filter((client) => client !== res);
    });
  }

  override async onEvent<T extends OB11EmitEventContent>(event: T) {
    const promises: Promise<void>[] = [];
    this.sseClients.forEach((res) => {
      promises.push(new Promise<void>((resolve, reject) => {
        res.write(`data: ${JSON.stringify(event)}\n\n`, (err) => {
          if (err) {
            reject(err);
          } else {
            resolve();
          }
        });
      }));
    });
    await Promise.allSettled(promises);
  }
}
